Dear Blizzard,
I had an idea because I feel that the team responsible for Warrior balance isn’t competent enough.
You should give every Mythic+ group that includes a Warrior a debuff that reduces the group’s DMG and Heal output, ensuring that this amazing class is finally fully balanced.
If I were in your place, I’d also remove the Tier Set bonus and prevent them from dealing DMG when targetNumber < 2.
After all, the class excels in single target too… 
(No words…)